Crypting in C#, C++, W32 api

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Dear experts
For educational purposes I'm trying to decrypt an encrypted text. This text is encrypted by .net using PasswordDeriveBytes with RijndaelManaged. Encrypted by .net means we have given:
　　　　passPhrase
　　　　saltValue
　　　　hashAlgorithm (SHA in my case)
　　　　passwordIterations
　　　　initVector
　　　　keySize

My target: I'm trying to decrypt the cipher text using only the basic W32 Api using pure c++ without any help the nice MS/VS support (decrypting the text by the help of full support of VS/.net is easy and works).

I'm facing now bigger problems especally with the "beast" "PasswordDeriveBytes". I have no idea what it is really doing, so I try to solve this part step by step. After googling hours my plan was/is:
I found
mono/PasswordDeriveBytes.cs at effa4c07ba850bedbe1ff54b2a5df281c058ebcb · mono/mono · GitHub[^]
the above link I hoped I found source code for "PasswordDeriveBytes" in c# which I can more or less easy transfer to c++.

But I stuck with an error message in "public override byte[] GetBytes(int cb)" line 243 (in the above link) with the message "Hash is not valid in the specified state.".

Finally my hope/question is, somebody has some similar experience in this and can give me a hint ir in best case a link for a c++ - "PasswordDeriveBytes" for dummies :)

I need to mention I' have no basic knowledge about this crypting stuff :(

Sorry for the cyrptic question and my english
Thank you in advance.
Regards

What I have tried:

Described above.。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。。

Posted 2-Feb-17 7:24am

User 11060979

Updated 2-Feb-17 8:46am

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Richard Deeming · Accepted Answer · 2017-02-02T08:46:00

This blog post[^] describes what the class is doing. It's essentially an implementation of PBKDF1, which might be a better search term to find a C++ implementation.

However, the documentation[^] says it's using an extension of PBKDF1. Without knowing exactly what that extension is, you'll probably struggle to match the output.

If you could switch the .NET code to use Rfc2898DeriveByes[^] instead, that would make your life simpler. It's a straight implementation of PBKDF2, with no extensions involved.

Alternatively, this StackOverflow answer[^] claims to be a working translation of the Mono code for PasswordDeriveBytes, albeit limited to the SHA1 algorithm.